The research outlined herein represents the first attempt to determine each of the relevant electrical stimulus parameters - current, voltage, and electrode-tissue interface resistance - necessary to elicit erection and ejaculation in the human male. The expertise of several disciplines, reproductive medicine, sexual therapy, physiology, and biomedical engineering, will be combined with the goal of developing rectal probe electrostimulation (RPE) as a practical method for semen collection in patients who, for a variety of reasons, are unable to produce specimens themselves despite apparent normal gonadal function. The relevant electrical parameters will be determined initially in healthy male volunteers. The techniques will then be applied to patients, especially those with spinal cord injuries or with impotence arising from physiologic causes. It is anticipated that, in the situation of married couples in which the male partner is having difficulty with erection and/or ejaculation, this study will provide a means of maintaining the sexual component of the marital unit and allow the fostering of progeny if desired. RPE may also be developed into a valuable diagnostic tool to be used in distinguishing between psychological impotence and physiologic impotence.